Melamine pyrophosphate [CAS Registry No. 13518-93-9]also called 1,3,5-triazine-2,4,6-triamine, pyrophosphate (2:1), is a known fire retardant additive for intumescent coatings. Certain disclosures exist in the prior art in regard to its method of manufacture.
U.S. Pat. Nos. 3,635,970 and 3,914,913 disclose mixing a pyrophosphate salt in water with melamine and a mineral acid. The mineral acid is present in sufficient amount to liberate pyrophosphoric acid from the pyrophosphate salt. The temperature of the reaction is preferably 75.degree. C. to 85.degree. C.
U.S. Pat. No. 3,920,796 discloses treatment of melamine phosphate in a calciner at 170.degree. C. to 325.degree. C. to form melamine pyrophosphate.